1. Field of the Invention
The invention relates to a technical field of liquid crystal display (LCD) panels and, more particularly, to a circuit for amplifying a display signal to be transmitted to a repair line by using a non-inverting amplifier and a liquid crystal display (LCD) device using the same.
2. Description of Related Art
FIG. 1 is a schematic illustration of an LCD panel with a repair line. The illustration includes an LCD panel 11, a first circuit board 12, a second circuit board 13, and a plurality of flexible packages 14 and 15 interposed between the LCD panel 11 and the first and the second circuit boards 12 and 13. Each flexible package 14 carries a source driver chip 141-143, and each flexible package 15 carries a gate driver chip 151-153.
As shown in FIG. 1, if a data line 171 connecting the data driver chip 141 is disconnected at point A, the display signal for the pixel before the point A is still provided by the data line 171. However, the display signal for the pixel after the point A is provided by the repair line 16 on the LCD panel 11.
Theoretically, the display signal transmitted by the data line 171 is equal to that transmitted by the repair line 16. However, the display signal transmitted by the repair line 16 is passed through the first circuit board 12 and the second circuit board 13, which causes a signal delay due to the long transmission path and the high transmission line impedance. Accordingly, in practice, the two display signals are not equal, and typically the display signal transmitted by the repair line 16 is lagged much behind that transmitted by the data line 171. In this case, insufficient charging to pixel display electrodes after the point A in a predetermined charging period may occur.
Typically, the predetermined charging period for the panel is decreased with increased resolution and increased area of the panel. The increased resolution makes the gate driver chip to have less time to turn on the TFT, and the increased area prolongs a signal transmission delay on the panel. Thus, the resolution and area of the panel can have an impact on the predetermined charging period. If the resolution of the panel is not changed, the signal transmission delay can determine a length of the predetermined charging period.
FIG. 2A is a schematic illustration of signal transmission delays occurred on the typical LCD panel 11. In FIG. 2B, it shows the delay of a display signal output by the data driver chip 144 of the region B in FIG. 2A. FIG. 2C indicates an effect of five-stage RC (resistor and capacitor) load on a metal line and ITO (indium tin oxide) glass, wherein the load generated is increased with the increased area of the LCD panel 11 of the region C in FIG. 2A. FIG. 2D shows the delay of a display signal output from the data driver chip to the TFT 21 of the region D in FIG. 2A. When a display signal is output from the data driver chip to region D, delay caused by regions B and C is included. In addition, the entire system of the LCD panel 11 can cause some delay effects, such as a transmission delay on the gate driver chip 154, an RC delay caused by an LC capacitor plus a turn-on resistor presented when an amorphous silicon metal oxide semiconductor (MOS) is turned on, and the like.
As cited, in FIGS. 1 and 2, the delay in the region C of the pixel driven by the repair line 16 on the LCD panel 11 is far greater than that generated in the pixel driven by a typical data driver chip normally. To overcome this, a solution is given by placing a unit buffer (also referring to as a voltage follower) in the data driver chip or on the first circuit board 12, which can reduce the delay. However, when an area of the LCD panel 11 is increased more and more, the transmission path of the repair line 16 on the panel 11 is prolonged more and more. Accordingly, the deformation of a display signal is increased sharply, and in this case, only using a voltage follower still has the signal deformation effect and is not enough to effectively improve the signal delay.
Therefore, it is desirable to provide an improved circuit to mitigate and/or obviate the aforementioned problems.